The present invention relates to the field of electronic displays and, in particular, to packages for field emission display ("FED") devices.
As the technology for producing small, portable electronic devices progresses, there is an increasing need for electronic displays that are small, provide good resolution, and consume small amounts of power. Low power consumption is important in order to provide extended battery operation.
Existing displays are generally constructed based upon cathode ray tube ("CRT") or liquid crystal display ("LCD") technology. However, neither of these technologies is ideally suited to the demands of small, portable electronic devices.
CRT's have excellent display characteristics, such as color, brightness, contrast, and resolution. However, they are also large, bulky, and consume power at rates that are incompatible with extended battery operation in portable computers.
LCD displays consume relatively little power and are small in size. However, by comparison with CRT technology, LCD displays provide poor contrast and permit a relatively limited range of viewing angles. Color versions of LCD's, like CRT's, tend to consume power at a rate that is incompatible with extended battery operation.
As a result of the deficiencies of CRT and LCD technology, efforts are underway to develop new types of electronic displays for electronic devices. One technology currently being developed involves the use of field emission displays ("FED"). FED's include large numbers of emitters formed on a baseplate. The emitters emit electrons, which strike a phosphor pattern (for example, dots) or monochrome layer on a faceplate, to produce the display.
FED's require a vacuum between the baseplate and the faceplate, in order to provide a dear path for the electrons travelling from the emitters to the phosphor. Ideally, the pressure between the baseplate and the faceplate is on the order of 10.sup.-12 Torr, or a "perfect" vacuum.
However, field emission displays typically only obtain vacuums on the order of 10.sup.-5 to 10.sup.-6 Torr, due to limitations in the conductance paths and pumps used to evacuate molecules in the space between the baseplate and the faceplate without external cycle times. For example, in a typical evacuation process, a mechanical pump is used to evacuate the display from atmosphere to a pressure on the order of 10.sup.-3 Torr. Then, a turbo-pump is used to decrease the pressure into the range of 10.sup.-5 Torr, and an ion pump is used to complete the process. However, some of the molecules in the display are inert, or electrically inactive, with low molecular weight, and do not pump easily. As a result, these particles are not removed by the turbo pump or the ion pump, and consequently are not removed from the package, creating higher partial pressure. Also, some molecules, such as water, tend to bind to the interior structure and components of the display, further contributing to higher partial pressure. These molecules typically are not removed completely in existing processes.
Therefore, there is a need for a process that will more completely evacuate a field emission display or similar package.